I. Field of the Invention
This invention pertains to mechanisms and systems for propelling an automobile having an engine with an output shaft. This invention also relates to hydraulic fluid systems, valves for such systems, and motors/pumps which are driven by or drive a rotating element by the force of hydraulic fluid pressure.
II. Description of the Prior Art
Machines driving a rotating driven element, especially automobiles have in the past employed a totally mechanical system for propulsion. Gears have been employed in both manual and automatic hydraulic transmissions to vary the torque output from the engine to the driven wheels. The invention discussed below represents a novel departure from this concept.
It has also become recently known that it is possible to drive a vehicle or other machine having rotating driven elements or wheels by the use of torque motors receiving fluid under pressure from a fluid pump. An especially good example of such vehicles and hydraulic drive systems is discussed in the November, 1977 issue of Mechanix Illustrated, pages 60-62, 151. However, for such propulsion systems of an automobile or other machine, there has been no control of the range of operation as is available with an automatic hydraulic transmission or a conventional manual transmission which varies the torque output from the engine by varying the gear ratio in the transmission. Since there is no control of the range of operation, the speed of the vehicle is limited since increased speed is achieved only by ever-increasing revolutions of the engine. Engine limitations and, likewise, limitations of the torque motors driving the wheels of such a vehicle necessarily limit the operation of the vehicle. Among other problems, the driving hydraulic fluid heats to dangerous temperatures under such circumstances.
A related problem in the prior art deals with turbine engines and the like used for driving automobiles. Such engines are known to have good efficiency at high constant rates of revolutions but significantly decreased efficiency when the rate of revolutions must be varied between a high and low operating point such as is necessary with an automobile. Significantly, it has been difficult to brake vehicles with turbine engines and a great number of devices have been directed to accomplishing the braking without generating excessive heat.
An exception to the type of engine discussed above is the ram jet engine disclosed in my copending U.S. patent application Ser. No. 142,022. The engine disclosed therein preferably uses water in the combustion chamber to take advantage of excessive heat of combustion.
The invention disclosed below is especially useful for overcoming the problem of braking vehicles having such engines since the driving torque motors act as braking pumps when unpressurized fluid is delivered to them.
Another significant problem with conventional vehicle drive systems is the loss of power between production in the engine and use at the driven wheels. This loss of power is inherent with conventional geared transmissions and is attributed chiefly to friction forces. Conventional geared transmissions typically transmit as little as 40% of the power supplied by the engine. It is generally accepted that hydraulic systems, on the other hand, are extremely power efficient. The problem of power loss is greatly diminished by use of the invention described below.
These and other problems of the prior art have been overcome by my invention discussed below and explained by means of a preferred embodiment.